1. Field of the Invention
The invention relates to a display device having an input for receiving an input video signal, a video signal processing circuit for processing the input video signal to an output video signal, said video signal processing circuit having an output for applying the output video signal to a display tube of the display device, a deflection unit for deflecting at least one video signal-dependent beam current generated in the display tube, and a correction circuit for correcting the video signal to be displayed.
2. Description of the Related Art
The invention also relates to a correction circuit.
A generally known system of improving the sharpness of a displayed (video) picture on a display screen is referred to as aperture correction. In this system the contours of an object are enhanced by means of an undershoot and an overshoot. Another generally known system of improving the sharpness of a displayed (video) picture on the display screen is referred to as scan velocity modulation. In this system the scan velocity of the electron beam currents is adapted in dependence upon the video signal so as to improve the (impression of) sharpness.
A display device in which the correction circuit includes a scan velocity modulator is known, for example from U.S. Pat. No. US-A 4,170,785. The derivative of the video signal is determined, whereafter a signal related to the derivative is applied to the scan velocity modulation coils for correcting/improving the (impression of) sharpness on the display screen.
A drawback of this display device known from said United States Patent is that the improvements only occur in given types of (video) pictures, whereas for other types of pictures the picture, displayed on the display screen is degraded.